The present invention is directed to manufacture of glassware, and more particularly to a method and apparatus for monitoring the functions of solenoid valves for applying final blow and finish cooling air through a dual-stage blowhead in the final blow operation of a glassware manufacturing machine.
Glassware, such as glass bottles, is typically made in a so-called individual section machine, which includes a plurality of identical sections that operate in synchronism and out of phase with each other to produce the glassware. Each section includes one or more blank molds, in which gobs of molten glass are either pressed or blown to form parisons. Each parison is then moved from the blank mold and placed in a final blow mold. A blowhead is lowered over the parison in the blow mold, and final blow air is directed into the parison through the blowhead to form the parison against the internal surface of the final blow mold. Conventional blowheads thus include an air passage for applying final blow air from an inlet to the inside of the parison. In dual-stage blowheads, also sometimes called isolated finish-cooled blowheads, finish cooling air is applied separately from the final blow air to cool the exterior surface of the container finish during application of final blow air and to prevent distortion of the finish under final blow pressure. Application of final blow air and finish cooling air in each machine section is controlled by an associated solenoid valve, which is responsive to valve control signals from machine timing electronics to apply final blow or finish cooling air to all blowheads in a machine section.
It is important in control of air-driven operations in a glassware manufacturing machine, including particularly application of final blow and finish cooling air through a dual-stage blowhead, to monitor operation of the solenoid valves to ensure that the air is being applied at the desired times relative to the valve control signals. This is conventionally accomplished by provision of multiple air pressure gauges at both ends of the glassware manufacturing machine, which must be monitored by the machine operating personnel. It is a general object of the present invention to provide an apparatus and method for electronically monitoring application of air (above or below atmospheric pressure) in a glassware manufacturing machine, including specifically application of final blow and finish cooling air to the dual-stage blockheads of each machine section, which automatically and electronically monitor timing of air application relative to the associated valve control signals for indicating operating condition of the various solenoid valves and detecting malfunction or impending malfunction at one or more of the solenoid valves.
Apparatus for monitoring application of air through a dual-stage blowhead to blow mold a container in a presently preferred implementation of the invention includes a first solenoid valve for applying final blow air through the blowhead to a container in a mold and a second solenoid valve for applying finish cooling air through the blowhead around the finish of the container in the mold. Electronic circuitry is coupled to the first and second solenoid valves for detecting the timing of application of first and second electrical valve control signals to the valves. Air pressure sensors are operatively coupled to the first and second solenoid valves for generating associated electrical sensor signals indicative of the timing of application of air by the first and second solenoid valves to the blowhead. Electronic compare logic is responsive to the timing of the valve control signals and the sensor signals for indicating operating condition of the valves, preferably by comparing timing of the valve control signals to timing of the sensor signals to indicate malfunction or potential malfunction at the valves. Potential malfunction at the valves may include failure of one or both of the valves to apply air responsive to the associated control signals, late operation of one or both valves to apply air responsive to the control signals, failure of one or both valves to terminate application of air responsive to the control signals, and late operation of one or both valves to terminate application of air responsive to the control signals.
A method of monitoring application of final blow and finish cooling air through respective first and second solenoid valves in accordance with another aspect of the invention includes detecting timing of electrical valve control signals applied to the first and second solenoid valves, and detecting timing of application of air by the first and second solenoid valves responsive to the valve control signals. The timings so detected are compared with each other, and operating condition of the valves is indicated as a function of such comparison.